Most undercarriages are hinged to an aircraft to move between a deployed position in which the undercarriage is supported by a side-brace member, and a folded position in which the undercarriage is received in a wheel bay of the aircraft. Undercarriages are known that include a raising actuator for raising the undercarriage into the wheel bay after takeoff. That actuator is generally in the form of a telescopic actuator.
The aircraft thus carries an actuator of non-negligible power, and thus presenting considerable weight, that is for use that is extremely brief, since it operates for no more than a few seconds during any one utilization cycle of the aircraft, i.e. while raising the undercarriage, and also while lowering it, essentially for the purpose of slowing down the downward movement of the undercarriage.
Proposals have also been made to fit at least one aircraft undercarriage with electric motors suitable for driving the wheels carried by the undercarriage so as to allow the aircraft to taxi independently without having recourse to thrust from its jets, thereby saving fuel.
Nevertheless, that equipment represents additional weight, which weight is also located in the vicinity of the wheels and thus at the end of the undercarriage, thereby increasing its inertia and contributing to increasing the forces involved in setting the wheels into rotation and the resilient return force to which the undercarriage is subjected on touching down.